Bench grinder



Aug. 18, 1964 G. w. MCCARTY ETAL 3,144,735

BENCH GRINDER Filed March 7, 1963 3 Sheets-Sheet 1 39 2 25 7 -1 56 n, 4, In 37 I 38 3e 35 as INVENTORS' GEORGE w. MCCARTY 73 MARTIN 1. SHEPS LAWRENCE H. BOWENJJI 36 36 ATTORNEY Aug. 18, 1964 G w MccARTY ETAL 3,144,735

' BENCH GRINDER Filed March 7, 1963 3 SheetsSheet 2 filming 1 o n N LE k II n'- o I E v- I t i J 1: r 535' W Y INVENTOR5 GEORGE W. MCCARTY m v MARTIN I SHEPS LAWRENC H. w I BY E 80 mm.

ATTORNEY ISQ g- 18, 1964 G. w. MOCARTY ETAL 3,144,735

BENCH GRINDER Filed March 7, 1965 3 Sheets-Sheet 3 Wm M INVENTORS GEORGE W. MCCARTY MARTIN I. SHEPS LAWRENCE H. BOWEN,1'JI

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ATTORNEY United States Patent 3,144,735 BENCH GRINDER George W. McCarty, Towson, and Martin I. Sheps and Lawrence H. Bowen III, Baltimore, Md, assignors to The Black and Decker Manufacturing Company,

Towson, Md a corporation of Maryland Filed Mar. 7, 1963, Ser. No. 263,567 7 Claims. (Cl. 51-166) The present invention relates to a stationary abrasive machine, and more particularly, to a bench grinder which may be manufactured easily and economically with a minimum of required parts and with a minimum of assembly time.

It is an object of the present invention to provide a stationary abrasive machine whose main housing is split vertically, that is to say, perpendicularly with respect to the axis of rotation of the rotor shaft, and comprises a pair of mating halves, each of which is identical to the other.

It is another object of the present invention to provide a stationary abrasive machine of the type which may be used in conjunction with an abrasive grinding wheel, a buffer or polisher, a sander, or a wire brush; and wherein the paramount design criteria are low-cost and ease of assembly, good performance and reliability of operation, and ease of maintenance and servicing.

It is a further object of the present invention to provide a stationary abrasive machine whose rotor shaft is journaled in bearings which are retained within respective bearing bosses during the assembly of the grinding wheels and guard members to the housing.

These and other objects of the present invention will become apparent from a reading of the following specification, taken in conjunction with the enclosed drawings, in which:

FIGURE 1 is a perspective view of the completed abrasive machine;

FIGURE 2 is a longitudinal section taken along the lines 2-2 of FIGURE 1, the tool rests and the brackets for the spark shields not appearing in the sectional view;

FIGURE 3 is a stepped section view taken along the lines 33 of FIGURE 2, showing the means for mounting the guard members to the motor housing;

FIGURE 4 is a fragmentary section view corresponding substantially to a portion of FIGURE 3, but with the particular guard member removed from the motor housing;

FIGURE 5 is a View showing the component parts of the machine in exploded relationship to each other;

FIGURE 6 is a schematic wiring diagram showing the electrical connections;

FIGURE 7 is a sectional view looking into the interior of the base portion of one of the identical mating halves of the motor housing, showing the base plate in assembled relationship to the motor housing.

FIGURE 8 is a plan view taken along the lines 38 of FIGURE 7, showing a detail of the means for mounting the machine to a bench or work table;

FIGURE 9 is a plan view taken along the lines 9-9 of FIGURE 7, showing a detail of the means for mounting the base plate and rubber feet to the motor housing;

FIGURE 10 is a fragmentary perspective view of the front of the base portion of the motor housing (the identical mating halves being shown assembled to each other) and with the caution plate shown in exploded relationship to the motor housing;

FIGURE 11 is a fragmentary perspective view, looking into the rear of the base portion of the motor housing shown in FIGURE 10; and

FIGURE 12 is a section view taken along the lines BJMJSS Patented Aug. 18, 1964 "ice 12-42 of FIGURE 10, showing the switch assembled to the machine.

With reference to FIGURE 1, there is illustrated a stationary abrasive machine 10 (ordinarily referred to in the trade as a bench grinder) and comprising a motor housing 11; a pair of rotating abrasive members, such as the grinding wheels 12; respective guard members 13a and 13b, which partially enclose the grinding wheels 12 for safety precautions; a pair of tool rests 14, one for each of the wheels 12, the tool rests 14 being horizontally adjustable for various diameters of grinding wheels (or to compensate for wear of the wheels) by means which includes a pair of wing nuts, one of which is shown as at 15; respective brackets 16 to which spark shields (not shown) may be secured; and a switch 17 for energizing the bench grinder It). It will be appreciated that in lieu of the grinding wheels 12, other types of rotating abrasive elements may be used, such as sanding wheels, bufiing or polishing wheels, or wire brushes, and that the teachings of the present invention are equally applicable to any type of rotating or abrasive members used in conjunction with a stationary machine. Moreover, suitable electric lights (not shown) may be mounted on the machine It), if desired.

With reference again to FIGURE 1, and with further reference to FIGURE 2, the motor housing 11 comprises a pair of identical mating halves 18 and 19, which are adapted to be joined together along a common vertical rnidplane (perpendicular to the axis of rotation) with the parting line between the halves 18 and 19 being designated as a A in FIGURE 1. Each of the mating halves 18 and 19 is preferably formed from die-cast aluminum; and inasmuch as the mating halves 18 and 19 are precisely identical to each other, both in the initial casting and in the subsequent machining, a considerable cost reduction is realized: first, in the initial outlays for the single die that is required (rather than for multiple dies); and

secondly, in the procurement of a greater volume of pieces at a reduced unit cost. Moreover, and as a result of the teachings of the present invention, a minimum of machining is required on the mating halves 18 and 19, and also, a minimum of assembly time is required for the overall machine It), thereby realizing additional savings in manufacture. The motor which is housed within the joined mating halves I55 and 19 is preferably of the induction type (one embodiment thereof rotating at 3600 rpm.) and comprises a stator 20 and a rotor 21 disposed in concentric relationship with respect to the stator 20. The

stator 20 is of the wound type and has stator laminations 22 (suitably stacked together) and a plurality of coils 23, the end portions of which project beyond the respective sides of the stack of laminations 22. The rotor 21, on the other hand, does not have any windings, but rather is of the fabricated type and comprises a central section 24, a shoulder 24a on either side thereof, and a series of circumferentially-spaced cooling fins 25 on each side of the shoulder 24a. The rotor 21 has a shaft 26 journaled for rotation in bearings 27 and 28. The bearings are suitably retained (in a manner hereinafter to be described in detail) within respective bearing bosses 29 and 30 formed within the mating halves 18 and 19, respectively. Preferably, but not necessarily, the bearings 27 and 28 are of the ball or other anti-friction type. The grinding wheels 12 have hubs 12a and are mounted upon the rotor shaft 26 by means of respective inner clamp members 31, outer clamp members 32, and lock nut 33, the latter engaging the respective threaded ends 34 of the rotor shaft 26. The rotor shaft 26 has an external annular groove 26a as a code so that the rotor 21 will always be inserted properly within the stator 20. The bottom of the bench grinder 10 has a suitable base plate 35 secured thereto (in a manner hereinafter to be described in detail), and a plurality of rubber feet 36 are disposed below the base plate 35. Moreover, a starting relay 37 is mounted upon the base plate and is confined within the base portion 38 of the motor housing 11 and is electrically connected to the stator 20 in a manner hereinafter to be described in detail.

With reference again to FIGURE 2, and with further reference to FIGURE 5, a pair of diametrically-opposite locating pins 39 are staked (or otherwise secured) to the stator 20, and the end portions of the pins 39 project beyond the stack of stator laminatins 22. Moreover, each of the identical mating halves 18 and 19 has a pair of internal bosses 40 formed therein, and the bosses 40 in both of the mating halves 18 and 19 are axially and circumferentially aligned with each other and with the pins 39 when the halves 18 and 19 are brought together in the assembly of the machine 10. Furthermore, each of the bosses 40 has a closed axial bore 41 to receive the respective end portions of the locating pins 39. A plug 42 of resilient material, such as rubber, is placed within the bosses 40 formed in the mating half 18, which may be referred to as the bottom half; and in the assembly of the bench grinder 10, the rubber plugs 42 are first placed within the bosses 40, and next the stator 20 is received within the mating half 18 such that the pins 39 are received within the respective bosses 40. The rotor 21 is fitted concentrically within the stator 20; and then the other mating half 19 (designated as the upper half) is secured to the bottom mating half 18 by means of a plurality of screws 43 and corresponding hexagonal locking nuts 44. Each of the locking nuts 44 is received within a hexagonal socket 45 (see FIGURES 3 and 4) formed within the mating halves 18 and 19. In the assembly of the mating halves 18 and 19, the rubber plugs 42 are compressed against the respective closed axial bores 41 in the bosses 40 of the mating half 18 and hence take up the tolerances in the assembly of the stator 20 within the motor housing 11.

With reference again to FIGURES 2 and 5, and with further reference to FIGURES 3 and 4, each of the guard members 13a and 131) has a central aperture 46 to allow the rotor shaft 26 to project therethrough, and it will be noted that the aperture 46 in the guard 13b is axially depressed in a direction away from the housing 11. The guards 13a and 13b are located or piloted by means of a pair of substantially-annular raised portions or ribs 11a (see FIGURES 3 and 4) which are formed externally on the motor housing 11. The outer race 27a of bearing 27 is clamped against the bearing boss 29 when the guard 13a (see FIGURES 3 and 4) is secured to the mating half 18 by means of the plurality of self-tapping screws 46a and lock washers 46b. Moreover, the inner race of bearing 27 is clamped between the respective inner clamping member 31 and the shoulder 47 formed on the rotor shaft 26. The other inner clamp member 31 clamps the inner race of the other bearing 28 against a corresponding shoulder 48 formed on the rotor shaft 26. Moreover, the bearing boss 30 has a hole 49 formed radially of the bearing 28, and a plug 50 of rubber or other resilient material is disposed between the outer race 28a of the bearing 28- and the respective bearing boss 30, thereby preventing the bearing 28 from turning within its respective hearing boss 30. The purpose of having the central aperture 46 for the guard 13b axially depressed away from the motor housing 11 is to absorb a tolerance build up in the assembly and subsequent servicing of the machine 10, yet at the same time the overall structure accommodates a secure retention of the bearings 27 and 28 for the rotor shaft 26; and thus a precision piece of equipment is obtained with a minimum of required machining, fitting, and assembly.

With reference to FIGURE 6, which is a schematic wiring diagram, the electrical connections are made from the line through the starting relay 37 and the switch 17 to the stator 20 in a manner understood by those skilled in the art.

With reference to FIGURE 7, which is a view looking into the interior of the mating half 18the two mating halves 18 and 19 being precisely identical to each other there is illustrated a pair of horizontal bosses 52 which are suitably apertured to receive the clamping screws 43 (see FIGURE 5) which hold the two halves 18 and 19 together. When the mating halves are brought together, the corresponding bosses 52 are in alignment with each other; and as previously noted, each of the bosses 52 has an external socket 45 which is preferably hexagonallyshaped so as to receive the hexagonal locking nut 44 therein for ultimate engagement with the screws 43. Moreover, a second pair of horizontal bosses 53 is formed Within each of the mating halves 18 and 19, and each of the bosses 53 has an internal hexagonal socket 54 within which the hexagonal head 55 of a screw 55a is staked in place or otherwise secured. The screws 55a project be yond the base portion 38 of the motor housing 11 (see FIGURE 10) for ultimate engagement with the wing nuts 15. The wing nuts 15 retain the tool rests 14 to the motor housing 11, see FIGURE 1, and the tool rests 14 are slidably guided within the tracks 51 formed within the base portion 38 as shown in FIGURES 2 and 5.

With reference again to FIGURE 7, and with further reference to FIGURES 8 and 9, a pair of internal vertical bosses 56 is formed in the mating half 18 (as well as the mating half 19) and each of the bosses 56 has a slotted aperture 57 (see FIGURE 9) which is substantially parallel to the base plate 35 and is accessible from within each of the halves. Moreover, each of the bosses 56 has a vertical opening 58 which communicates with its respective slotted aperture 57 and with an opening in the base plate 35. A plurality of feet 36 are provided, one for each of the bosses 56; and preferably, but not necessarily, the feet 36 are molded from rubber. Each of the feet 36 is provided with an axial opening 60, and a locking nut 61 is squeezed within (or suitably trapped within) the opening 60 of each of the feet 36. A screw 62 is provided for each of the locking nuts 61. Each of the screws 62 has a head which is slidably received within (and is thereafter trapped within) a respective one of the slotted apertures 57 prior to the assembly of the base plate 35 to the motor housing 11. Each of the screws 62 passes through a respective one of the vertical openings 58 and through a respective one of the feet 36 to engage its respective locking nut 61 and hence retain the base plate 35 to the motor housing 11, and simultaneously therewith, to secure the rubber feet 36 to the underside of the bench grinder It). A second internal vertical boss 63 is formed in each of the mating halves 18 and 19 intermediately of the pair of first vertical bosses 56. Consequently, the assembled bench grinder 10 may be suitably clamped to a table T (or work bench or pedestal) by means of a screw 64, the head of which may be inserted through a keyhole slot 35a (see FIGURE 8) formed in the base plate 35. The screw 64 is then moved radially outwardly so that its head is slidably received within (and is thereafter trapped within) the slotted aperture 65 formed in the vertical boss 63. Once the screws 64 are thus in place, the bench grinder 10 may be secured to the table T by means of the washers 66 and clamping nuts 67.

With reference to FIGURES 10 and 11, each of the identical mating halves 18 and 19 includes the base portion 38 which comprises a pair of outwardly-flanged substantially-fiat portions 68 and a pair of substantiallyvertical skirt portions 69 depending therefrom. Each of the outwardly-flanged portions 68 has an opening 70 (preferably rectangular) formed both in the back and in the front of the machine. Moreover, each of the skirt portions 69 has an opening 71 (preferably semi-circular) formed in the skirt portions 71. When the mating halves 18 and 19 are joined together, the openings 70 and 71 in one of the halves will communicate with the corresponding openings in the other of the mating halves 19, at the common vertical midplane A, to form double pairs of complete openings, one pair of which is in the outwardly-flanged portions 68, and the other pair of which is in the skirt portions 69. The switch 17 is mounted within one of the pairs of openings 70 at the front of the machine, see FIGURE 10, while the conventional electrical cord 72 and its cord protector 72a, see FIGURE 11, is received within one of the pairs of openings 71 at the back of the machine. As shown more clearly in FIG- URE 12, the switch 17 is secured to the motor housing 11 by means of a cover plate 75, screws 76, and ears 77, the latter having tapped holes to receive screws 76. Moreover, and as further shown in FIGURES l and 11, the remaining circular opening 71 (at the front of the machine) may be covered by a suitable caution plate (conventional for apparatus of this nature) while the other rectangular opening 70 at the rear of the machine (see FIGURE 11) may be suitably covered by a nameplate 74.

Thus it will be appreciatd that inasmuch as the motor housing 11 is split vertically into two mating halves 18 and 19, each of which is identical to the other, a savings is realized, not only in the initial outlays for tools and dies, but also in the reduced amount of subsequent machining of the castings and in the simplified assembly of the overall machine 10. The only machining which is required is to bore out the bearing bosses 29 and 30, to machine the bores 41 for the pins 39, and to face off the castings at the parting line A (which may be combined in one operation) and to drill the hole 49 for the bearing plug 50. Further handling and inventory of the castings is also simplified inasmuch as the castings are identical to each other, that is to say, there is not a right and a left hand casting to be separately handled and stored.

Moreover, the overall method of assembly of the bench grinder 10, and in particular, the method of retaining the bearings 27 and 28, results in a low-cost readily-producible machine, yet one which is a precision piece of equipment and is capable of providing reliable service and performance for extended periods of time.

Obviously, many modifications may be made without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.

We claim:

1. A stationary abrasive machine, comprising:

(a) a split-housing including a pair of completely identical mating halves interchangeable with each other, and join together along a common vertical midplane;

(b) means to detachably secure said mating halves together;

(c) a motor including a stator and a rotor arranged concentrically within said stator;

(d) means to locate and trap said stator between said mating halves as said halves are secured together; (e) said rotor having a shaft arranged perpendicularly with respect to said common vertical midplane;

(f) a bearing retained within each of said pair of mating halves for journaling said rotor shaft within said housing, each of said bearings having an inner race and an outer race;

(g) said shaft having respective end portions projecting beyond each of said mating halves of said housing;

(h) a rotating abrasive member secured to each of said respective end portions of said shaft;

(1') means to clamp the inner race of each bearing against a respective shoulder formed on said rotor shaft;

(j) a pair of guard members, one for each of said abrasive members; and

(k) means to clamp the outer race of at least one of said bearings against the respective half of said housing and adjacent said respective guard member.

2. The machine as described in claim 1, wherein said means to locate and trap said stator between said mating halves, as said halves are secured together, comprises:

(a) a pair of circumferentially-spaced pins secured to said stator;

(b) each of said pins having respective end portions 10 projecting beyond said stator;

(c) a pair of circumferentially-spaced bosses formed within each of said mating halves of said split-housing, said bosses being aligned with each other and with said pins when said halves are brought together;

(at) each of said bosses in each of said halves having a closed axial bore to receive said respective end portions of said pins; and

(e) a plug of resilient material in the respective bores of each of said pair of bosses in at least one of said mating halves, said plugs being disposed between said respective bores and a respective end portion of each of said pins.

3. The machine as described in claim 1, wherein a base plate is provided, and wherein means are further provided to secure said base plate to the underside of said split-housing after said halves are secured together; said means comprising: i

(a) a pair of spaced-apart bosses formed within each of said mating halves;

(b) each of said bosses having a slotted aperture, substantially parallel with said base plate, and accessible from within said halves;

(0) each of said bosses further having a vertical opening which communicates said respective slotted apertures with said base plate;

(d) a plurality of feet, one for each of said bosses;

(e) said feet each having an axial opening formed therein;

(3) a locking nut retained within each of said feet;

and

(g) a screw for each of said locking nut;

(h) said screws each having a head trapped within a respective one of said slotted apertures prior to the assembly of said base plate to said housing, and each of said screws passing through a respective one of said vertical openings and through a respective one of said feet to engage a respective one of said locking nuts.

4. The machine as described in claim 1, wherein:

(a) each of said identical mating halves of said splithousing includes a base portion having a pair of outwardly-flanged substantially-flat portions and further having a pair of substantially-vertical skirt portions depending therefrom; and wherein (b) each of said identical mating halves is provided with an opening in each of its pair of outwardlyflanged portions and with an opening in each of its pair of skirt portions;

(0) the openings in one of said halves communicating with the openings in the other of said halves, at the common transverse midplane and when said halves are joined together, to form dual pairs of complete openings, one pair in said outwardly-flanged portions, and the other pair in said skirt portions;

(d) a switch mounted within one of said openings in said outwardly-flanged portions;

(e) an electrical cord passing through one of said openings in said skirt portion, on the side of the machine 70 which is opposite from said switch; and

( means to cover the two remaining openings which are not being used.

5. A stationary abrasive machine comprising:

(a) a housing;

75 (b) a motor within said housing;

(c) said motor including a shaft having respective end portions extending from either side of said housings;

(d) a rotating abrasive member detachably secured on each of said respective ends of said motor shaft;

(e) a pair of guard members secured to said housing, one for each of said rotating members, and partially enclosing said rotating members;

(f) each of said guard members having a central aperture for the passage of said motor shaft therethrough;

(g) a pair of bearing bosses formed in said housing, one on each side thereof, and adjacent to said respec tive central apertures in said guard members;

(11) a bearing in each of said bearing bosses, and each of said bearings having an inner race and an outer race;

(i) a pair of shoulders formed on said motor shaft, one each adjacent a respective one of said bearing bosses;

(j) a clamp member between each of said rotating abrasive members and said inner race of said respective bearings, thereby securing said bearings against said respective shoulders when said rotating abrasive members are secured to said motor shaft;

(k) one of said guard members clamping said outer race of a respective one of said bearings, against said respective bearing boss in said housing, when said one guard member is secured to said housing; and

(I) said other of said guard members being axially depressed about its respective central aperture and away from said housing, whereby said other of said guard members is out of engagement with the outer race of the other of said bearings.

6. The machine as described in claim 5, wherein:

(a) means are provided to prevent said other bearing from turning in relation to its respective bearing boss;

(b) said means comprising a plug of resilient material compressed between said respective bearing boss and the outer race of said other bearing.

7. A stationary abrasive machine, comprising:

(a) a split-housing having a pair of identical mating halves, completely interchangeable with each other, and means to detachably secure said halves together along a common vertical midplane;

(b) a motor comprising a stator and a concentric rotor having a shaft arranged transversely of said common vertical midplane;

(c) rotary abrasive members carried on the respective ends of said shaft;

(d) means to locate and trap said stator between said mating halves as said halves are secured together;

(2) a switch wired electrically with said motor and the line, and means to trap said switch between said mating halves as said halves are secured together;

(f) each of said halves having an outer side wall formed with a bearing boss;

(g) a bearing in each of said bosses for journaling said rotor shaft, each of said bearings having an inner race and an outer race;

(11) means to clamp the inner race of each of said bearings against a respective shoulder formed on said rotor shaft; and (i) means to retain the outer race of each of said bearings within said respective bearing bosses.

References Cited in the file of this patent UNITED STATES PATENTS 1,332,009 Sumbling Feb. 24, 1920 1,587,865 Schneider June 8, 1926 1,631,247 Conradson June 4, 1927 1,743,134 Homnoud et al Jan. 14, 1930 1,923,760 Smith Aug. 22, 1933 2,288,579 Anes June 30, 1942 FOREIGN PATENTS 435,048 Italy May 7, 1948 

1. A STATIONARY ABRASIVE MACHINE, COMPRISING: (A) A SPLIT-HOUSING INCLUDING A PAIR OF COMPLETELY IDENTICAL MATING HALVES INTERCHANGEABLE WITH EACH OTHER, AND JOIN TOGETHER ALONG A COMMON VERTICAL MIDPLANE; (B) MEANS TO DETACHABLY SECURE SAID MATING HALVES TOGETHER; (C) A MOTOR INCLUDING A STATOR AND A ROTOR ARRANGED CONCENTRICALLY WITHIN SAID STATOR; (D) MEANS TO LOCATE AND TRAP SAID STATOR BETWEEN SAID MATING HALVES AS SAID HALVES ARE SECURED TOGETHER; (E) SAID ROTOR HAVING A SHAFT ARRANGED PERPENDICULARLY WITH RESPECT TO SAID COMMON VERTICAL MIDPLANE; (F) A BEARING RETAINED WITHIN EACH OF SAID PAIR OF MATING HALVES FOR JOURNALING SAID ROTOR SHAFT WITHIN SAID HOUSING, EACH OF SAID BEARINGS HAVING AN INNER RACE AND AN OUTER RACE; (G) SAID SHAFT HAVING RESPECTIVE END PORTIONS PROJECTING BEYOND EACH OF SAID MATING HALVES OF SAID HOUSING; (H) A ROTATING ABRASIVE MEMBER SECURED TO EACH OF SAID RESPECTIVE END PORTIONS OF SAID SHAFT; (I) MEANS TO CLAMP THE INNER RACE OF EACH BEARING AGAINST A RESPECTIVE SHOULDER FORMED ON SAID ROTOR SHAFT; (J) A PAIR OF GUARD MEMBERS, ONE FOR EACH OF SAID ABRASIVE MEMBERS; AND (K) MEANS TO CLAMP THE OUTER RACE OF AT LEAST ONE OF SAID BEARINGS AGAINST THE RESPECTIVE HALF OF SAID HOUSING AND ADJACENT SAID RESPECTIVE GUARD MEMBER. 